Communication based services are based on interaction between at least two communicating endpoints. Typically a service operation involves a series of messages exchanged between the communicating endpoints and the amount of communicated information is relatively high. In some service applications, however, the amount of information exchanged at one time is very small.
For example a tracking service is a communication-based service that involves a tracking device used as user equipment by the subscriber of the service, and a control node. The control node and the user equipment need to exchange information and therewith trigger service operations in one end or in both ends. The amount of exchanged information at one time is fairly small, for example from the user end to the control node:                scheduled system message indicating location of the user equipment        scheduled system message indicating battery status of the user equipment        entry or departure message of a known location        alarm based on breach of condition.Correspondingly, information from the control node may comprise:        a request for an unscheduled report or measured value        information on a parameter to be changed.        
Conventional tracking services apply short messages, General Packet Radio Service (GPRS) transmissions or circuit switched data calls to deliver the required messages. None of these are actually ideally suited for the purpose.
Short messages represent a variety of store and forward type of messaging services, where the message is first delivered to a short message system centre and the centre delivers the message to the targeted endpoint. The short messages are easy to compose and manage and they are widely used in services, especially in tracking services. However, the delivery of short messages may be delayed due to, for example, congestion in the network or in the short message centre. Typically in critical situations and major holidays the short message centres are not able to handle all the traffic. In some services, including the advanced tracking services, such delays are not acceptable.
The problem with GPRS-based communication is that the handshake process required for assigning a unique IP address for the user equipment and passing this IP address to the control node consumes relatively long period of time. The user equipment needs to be in an active mode during these operations, which means that the power consumption increases significantly when the amount of transmissions gets higher. The same problem concerns circuit switched data calls, where the wireless transmitter needs to be on during the duration of the data call. High power consumption is in general an highly disliked feature, and in tracking devices where the dimension of the apparatus is a critical factor for the service it may be the decisive issue that mandates whether a service succeeds or not.
Furthermore, these conventional communication mechanisms are typically charged on a rate basis. However, subscribers of the tracking services are typically not willing to commit to operations where they do not have a direct control to the amount of transmitted messages, meaning to the size of their monthly bill. Mechanisms that would better adjust to flat fee charging are continuously looked for.